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2010-04-09 Chris Allegretta <chrisa@asty.org> 

* files.c (do_writeout): Better security fixes for backup file writing, 
          mangled from submission by Dan Rosenberg <dan.j.rosenberg at gmail>.



git-svn-id: svn://svn.savannah.gnu.org/nano/trunk/nano@4496 35c25a1d-7b9e-4130-9fde-d3aeb78583b8
master
Chris Allegretta 2010-04-09 15:01:51 +00:00
parent dbbf9a052f
commit 7f61a6cb79
2 changed files with 28 additions and 18 deletions
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6
ChangeLog
View File

@ -1,4 +1,8 @@
2010-04-02 Chris Allegretta <chrisa@asty.org> 2010-04-09 Chris Allegretta <chrisa@asty.org>
* files.c (do_writeout): Better security fixes for backup file writing,
mangled from submission by Dan Rosenberg <dan.j.rosenberg at gmail>.
2010-04-08 Chris Allegretta <chrisa@asty.org>
* files.c (do_writeout): Previous fixes should not cause a crash * files.c (do_writeout): Previous fixes should not cause a crash
when saving a new file. Discovered by Mike Frysinger <vapier@gentoo.org>. when saving a new file. Discovered by Mike Frysinger <vapier@gentoo.org>.

38
src/files.c
View File

@ -1515,11 +1515,11 @@ bool write_file(const char *name, FILE *f_open, bool tmp, append_type
if (ISSET(BACKUP_FILE) && !tmp && realexists && ((append != if (ISSET(BACKUP_FILE) && !tmp && realexists && ((append !=
OVERWRITE || openfile->mark_set) || OVERWRITE || openfile->mark_set) ||
openfile->current_stat->st_mtime == st.st_mtime)) { openfile->current_stat->st_mtime == st.st_mtime)) {
int backup_fd;
FILE *backup_file; FILE *backup_file;
char *backupname; char *backupname;
struct utimbuf filetime; struct utimbuf filetime;
int copy_status; int copy_status;
struct stat backupst;
/* Save the original file's access and modification times. */ /* Save the original file's access and modification times. */
filetime.actime = openfile->current_stat->st_atime; filetime.actime = openfile->current_stat->st_atime;
@ -1589,26 +1589,35 @@ bool write_file(const char *name, FILE *f_open, bool tmp, append_type
sprintf(backupname, "%s~", realname); sprintf(backupname, "%s~", realname);
} }
if (stat(backupname, &backupst) != -1 && /* First, unlink any existing backups. Next, open the backup
(backupst.st_uid != st.st_uid)) { file with O_CREAT and O_EXCL. If it succeeds, we
statusbar(_("Error writing backup file %s: File owner mismatch"), backupname, have a file descriptor to a new backup file. */
if (unlink(backupname) < 0 && errno != ENOENT) {
statusbar(_("Error writing backup file %s: %s"), backupname,
strerror(errno)); strerror(errno));
free(backupname); free(backupname);
goto cleanup_and_exit; goto cleanup_and_exit;
} }
backup_fd = open(backupname, O_WRONLY | O_CREAT | O_APPEND,
S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH);
/* Now we've got a safe file stream. If the previous open()
call failed, this will return NULL. */
backup_file = fdopen(backup_fd, "wb");
/* Open the destination backup file. Before we write to it, we if (backup_fd < 0 || backup_file == NULL) {
* set its permissions, so no unauthorized person can read it as statusbar(_("Error writing backup file %s: %s"), backupname,
* we write. */ strerror(errno));
backup_file = fopen(backupname, "wb"); free(backupname);
goto cleanup_and_exit;
if (backup_file == NULL || chmod(backupname, }
openfile->current_stat->st_mode) == -1) {
if (fchmod(backup_fd, openfile->current_stat->st_mode) == -1 ||
fchown(backup_fd, openfile->current_stat->st_uid,
openfile->current_stat->st_gid) == -1 ) {
statusbar(_("Error writing backup file %s: %s"), backupname, statusbar(_("Error writing backup file %s: %s"), backupname,
strerror(errno)); strerror(errno));
free(backupname); free(backupname);
if (backup_file != NULL)
fclose(backup_file); fclose(backup_file);
/* If we can't write to the backup, DONT go on, since /* If we can't write to the backup, DONT go on, since
whatever caused the backup file to fail (e.g. disk whatever caused the backup file to fail (e.g. disk
@ -1625,10 +1634,7 @@ bool write_file(const char *name, FILE *f_open, bool tmp, append_type
copy_status = copy_file(f, backup_file); copy_status = copy_file(f, backup_file);
/* And set its metadata. */ /* And set its metadata. */
if (copy_status != 0 || chown(backupname, if (copy_status != 0 || utime(backupname, &filetime) == -1) {
openfile->current_stat->st_uid,
openfile->current_stat->st_gid) == -1 ||
utime(backupname, &filetime) == -1) {
if (copy_status == -1) { if (copy_status == -1) {
statusbar(_("Error reading %s: %s"), realname, statusbar(_("Error reading %s: %s"), realname,
strerror(errno)); strerror(errno));